Fluid coupling for mobile equipment

ABSTRACT

In an assembly including a diesel engine, a fluid coupling connected to the flywheel of the diesel engine, a comminuting machine and a conveyor for feeding the comminuting machine, a fluid coupling module is common to various output power train assemblies. Slip speed of the fluid coupling between impeller input and runner output shafts is measured, and modulates or regulates the process feed rate of the conveyer. An electrically actuated control valve acts as an oil flow diverter valve directing oil into the fluid coupling impeller when a signal to engage the coupling is given, and in response to a signal from an over-temperature sensor when the temperature of circuit oil leaving the element exceeds a preset set point value, diverts the oil to a reservoir, thereby permitting the impeller and runner cavity to evacuate, which separates the engine from the load.

CROSS REFERENCE TO RELATED APPLICATION

This is a division of application Ser. No. 10/171,125 entitled FluidCoupling for Mobile Equipment, which was filed on Jun. 13, 2002 now U.S.Pat. No. 6,769,248 and which is incorporated herein by reference.

STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH OR DEVELOPMENT

Not Applicable.

BACKGROUND OF THE INVENTION

This invention has to do with a fluid coupling for use on dieselengine-driven mobile equipment such as wood chippers, rock crushers,road surface grinders (also known as scarifiers or road millers), andthe like comminuting mills. This comminuting mill equipment is typicallyused in conjunction with feedstock conveyors, or in the case of the roadsurface grinder, used in conjunction with a method to move the grinderalong the road to be ground. For controlling the speed and connectingand disconnecting the mills and engines, there are four types of clutchin common use. Three types can be engaged and disengaged with the enginerunning: a mechanical clutch, a hydraulically operated mechanicalclutch, and a fluid coupling. One type must be engaged with the driverstopped and it is usually disengaged with the driver running: amechanical torque limiter. The feedstock conveyors, or drivingmechanisms of road grinders, are typically driven separately byhydraulic motors via hydraulic pumps that are mounted on and powered bythe diesel engine, the conveyors being controlled by a manual controlvalve remotely operated by the operator of the mobile equipment.Heretofore, with a mechanical clutch, the conveyors have been run at aconstant speed that may be set by the operator or at a speed that isdirectly proportional to engine speed. Because the hydraulic pumps andmotors are positive displacement; if a jam develops in the mill, theoperator operates the control valve to the reverse position, thefeedstock conveyor stops and backs up for several seconds at the samespeed as it goes forward, and then when the operator observes that themill is cleared, the operator manually puts the valve into forwardposition and the conveyor returns to a normal forward feeding rate. Aproblem with this combination of a mechanical clutch and a manuallyoperated conveyor or road grinder is that the operators reaction time isslow, compounded because the operator has much equipment to operatesimultaneously, and therefore, it is relatively easy to jam a mill to acomplete stop. If such a quick and immediate stop occurs, the dieselengine, especially certain susceptible components, such asturbochargers, can be expected to be damaged, often requiring repairsbefore restart.

These problems of damage to the diesel engine and its susceptiblecomponents are generally tolerable when the diesel engines being usedare only up to 300 hp. However, the problems that result from a quickand immediate stop are exacerbated as the diesel engine sizes increaseto the current levels of 1000 to 1500 HP and as the new electronicallycontrolled fuel systems are introduced that measurably increase thepower ratings of diesel engines without significantly changing thephysical size and without significantly changing the physical strengthof the engines.

Mechanical clutches have been widely used in such diesel engine drivenmobile equipment applications. A mechanical clutch mechanism, such asmanufactured and supplied by Twin Disc, Inc. of Racine, Wis., is mountedonto the flywheel housing of a diesel engine. In such a manuallyoperated mechanical clutch, a lever is used to operate the clutch packand requires an operator to be next to the diesel engine and clutchhousing while engaging and disengaging the clutch. This arrangementfunctions reasonably well except when a very hard object or a largeamount of feedstock is fed into the comminuting mill, for example, ahammer mill, and the hammer mill becomes overloaded and jams. In thiscase, the belts driving the hammer mill slip and wear, the bearingsbecome overloaded, and the diesel engine stops almost instantaneously.This damages the bearings, the belts, the clutch, the diesel engine, andthe turbocharger for the diesel engine.

As a mechanical clutch is used over time, the surfaces of the clutchplates wear and the linkage needs to be adjusted to make certain theclutch can be fully disengaged at one end of the clutch lever throw andfully engaged at the other end of the clutch lever throw. If the clutchcannot be fully disengaged, then a considerable amount of power canstill be transmitted and the clutch plates will get very hot andpossibly become severely damaged. If the clutch cannot be fully engaged,then the clutch will slip at high-power conditions and wear rapidly.Because lever activated mechanical clutches require the operator to besituated very close to the diesel engine, clutch, sheave and belts orother load equipment when the lever is actuated to engage and/or todisengage the load equipment, if the high-powered mechanical equipmentbreaks, parts may be thrown about and pose grave risk to the operator.Hydraulically operated mechanical clutches that use a lever operatedmaster hydraulic cylinder and a slave hydraulic cylinder to operate theclutch permit the operator to be further removed, but the rest of theproblems remain.

Another version of an hydraulically actuated mechanical clutch is onewherein the mechanical clutch pack is compressed and thereby engaged bymeans of hydraulic pressure, and the hydraulic pressure is controlled byan electronic controller, such as manufactured by Power TransmissionTechnology, Inc., of Ohio. In normal operation, the electroniccontroller, which is remote from the clutch, can be manually given asignal to engage, and the controller causes hydraulic pressure to act,engaging the clutch. Similarly, a manual signal to the controller cancause the hydraulic pressure to be released, and the clutch pack isreleased and almost no power is transmitted through the clutch. Underabnormal conditions such as a jam that develops over several seconds,the electronic controller, essentially a dedicated digital computerbased controller, can sense a decrease in speed, and the controller canrelease the clutch pack and attempt to reengage the clutch a series oftimes. After a preset number of attempts to reengage the mill whereinthe speed of the output shaft of the clutch does not increase to enginespeed, the electronic controller will decide that the mill is jammed,and the controller can cause the clutch pack to remain released. Insummary, this type of electronically controlled, hydraulically actuatedmechanical clutch (a) in the case of a jam that develops over severalseconds, can separate the engine from the mill when the mill is jammed,saving the engine and its susceptible components from damage, but, inthe case of an instantaneous jam, cannot separate the engine from themill fast enough to avoid stopping the engine and damaging susceptiblecomponents, and (b) can sense when there is too much wear of the clutchparts to assure full engagement, and can separate the engine from themill in this case, or once separated, can maintain separation of theengine from the mill. However, this type of hydraulically actuatedmechanical clutch suffers from the problem of all mechanical clutches:From time to time and depending upon operator care and the types of dutyto which the mill is subjected, the transmission must be disassembledand the worn clutch plates must be replaced.

For lower power equipment, below perhaps 300 hp, mechanical clutches donot wear much during normal engagement and normal disengagement.However, as the power transmitted increases to the current levels of1000 to 1500 hp, the wear of mechanical clutches during normalengagement and normal disengagement increases to the point that it isnoticeable and is a concern. Due to the wear during normal engagementand normal disengagement, and due to the possibility of shearing shaftsand couplings during a quick engagement event and throwing these partsabout, it is common practice for manufacturers of all sizes ofmechanical clutches to provide signs to be mounted on the equipment andvisible to the operators, that the clutches must be engaged when theengine is operating at idle speed, and not above idle speed, andparticularly, not at the normal running speed which is well above idlespeed.

In recent years, mechanical torque limiters have been introduced andused to separate the engine from the mill in the case of a jam in themill. A mechanical torque limiter is a mechanical device that can bemounted on the end of the output shaft of the mechanical clutch indirect drive arrangements. They can also be used with side loadapplications, and they function as described here. In a mechanicaltorque limiter, a housing part mounted on the driving shaft contains aseries of radial or axial pins backed by springs and the mating part, adriven part, is attached to the driven shaft; this driven part havingdetents into which the ends of the pins are seated. The housing part andthe driven part are held concentric to each other by rolling elementbearings. When an over torque condition occurs, the pins slide up fromthe bottom of the deep-end groove and the springs overload andfunctionally break away, causing the two parts of the mechanical torquelimiter to separate mechanically so that torque can no longer betransmitted from one part to the other part. For safety, the springs andpins of the mechanical torque limiter are retained in the housing part.After the driver is stopped, the springs and pins of the mechanicaltorque limiter can be manually reset. After the hammer mill is cleared,the diesel engine can be started and the equipment put back intoservice. The pins, detents, and rolling element bearings do experiencesome wear during each separation event, and therefore, they can beexpected to require reconditioning maintenance from time to time, withthe frequency in proportion to the severity of the duty.

Fluid drives for stationary equipment have been in service for severalyears, with the earliest ones being developed in approximately 1905.Three well-known manufacturers of this equipment today are TurboResearch, Inc (of the USA), Voith (of Germany) and Transfluid (ofItaly). Three broad categories are (1) variable speed fluid drives, (2)constant speed fluid couplings that, after the start-up period on theorder of seconds, have no means for any significant variance of theoutput speed which is slightly less than the speed of the driver, and(3) fluid couplings for which the output speed is either nearly zero orslightly less than the speed of the driver, and can be repeatedly cycledbetween these two states by operation of an oil flow control valve whichcontrols the flow of circuit oil, respectively, by either bypassing oilto the reservoir in the “off” state or by directing oil to the fluidcoupling in the “on” state. Such a control valve may also be referred toas a diverter valve.

Variable speed fluid drives of type (1) above are described in U.S. Pat.Nos. 5,331,811, 5,315,825, and 5,303,801, and are manufactured by TurboResearch, Inc. and Voith. These patents are referenced to provideextensive background on fluid drive technology, since variable speeddrives are not the subject of the present discussion.

Fluid couplings for stationary equipment identified as type (2) abovehave been in service for several years, particularly on stationary motordriven equipment, such as mills and conveyors. Two well-knownmanufacturers of this type are Voith (of Germany), and Transfluid (ofItaly), represented by Kraft in the USA.

One of the most common forms of type (2) fluid couplings isself-contained, and has all of the circuit oil stored in it. One part ofthe fluid coupling, the impeller and impeller casing assembly, whichforms the entire outer shell, is mounted on an end of a motor shaft. Thedriven portion, including a runner, is mounted onto the shaft of thedriven equipment such that the runner is inside the impeller andimpeller casing assembly. These fluid couplings, which are almostinvariably designed and manufactured with the impellers, runners, andcasings made from aluminum for reasons which include lower weight andlower cost, have a series of fuse plugs mounted in the outer periphery.These fluid couplings are intended to be used for “soft-start”conditions, and are not expected to be used where jams are to beencountered, though occasionally jams are encountered. Often this typeof fluid coupling has two functional chamber for containing oil, onechamber containing most of the oil when the fluid coupling is stopped,and a second chamber which is the fluid coupling chamber that containsthe impeller and runner vaned structures used for transmitting torquefrom the impeller to the runner. Once the motor is started, oil movesfrom the storage chamber to fill the fluid coupling chamber containingthe impeller and runner with oil and the oil can not be removed from thefluid coupling chamber without (a) either shutting down the motor or (b)opening (melting) the fuse plugs. When this type of fluid coupling isstopped under normal circumstances, the oil drains from the fluidcoupling chamber back to the storage chamber. When in operation, heat isgenerated in the fluid coupling in proportion to the slip speed betweenthe input shaft speed and the output shaft speed, and the slip speedincreases in direct proportion to the torque transmitted. In normaloperation, the cooling fins that are cast into the outer surface of theimpeller and casing dissipate to the surrounding air the heat generatedby the fluid slip process. Should the equipment become overloaded, orthe load equipment jam, much heat will be generated in the oil and inorder to protect the load equipment as well as to protect the aluminumparts of the fluid coupling from failing, the fuse plugs will melt,permitting the oil to be spewed out of the rotating impeller casinguntil empty, and this separates the load equipment from the motor, andthe motor will operate essentially unloaded until it is shut down.Several gallons of very hot oil typically are spilled in such an event.This is dangerous for personnel in the area, can be a fire hazard, and,today, depending upon the amount of oil spilled in such an eventoccurring in the United States, it may well be a reportable event to theUnited States Environmental Protection Agency (EPA). Due to these safetyand environmental issues, Turbo Research, Inc. has not manufactured thistype of equipment.

A subsequent version of this equipment by Voith, and Transfluid for usewith mobile equipment included a sealed external housing around therotating element and oil circulating pumping and cooling equipment. Thefluid coupling impellers, runners, and casings are still made from castaluminum with the vanes being thin, and the impellers or impellercasings contain the fuse plugs so that during an overload event the fuseplugs melt, the oil spews out of the rotating element limiting thetemperature to which the aluminum parts are exposed and the duration ofthe exposure, but the oil is contained in the sealed external housingand is not lost. The diesel engine can be stopped under a controlledstop sequence without damage. However, in order to be able to run again,the external housings of this design have to be opened and the fuseplugs have to be replaced. The fuse metal is contained somewhere in theoil reservoir, and unless the reservoir is completely cleaned out, thefuse metal can be drawn into the oil pump with the normal suction oilflow, and therefore, potentially, the fuse metal can pose problems tothe oil circulating pump.

Fluid couplings of type (3) above are the primary focus of thisdocument. Turbo Research, Inc., Voith and Transfluid have developedfluid couplings which can be turned on and off by changing the state ofan oil flow control diverter valve, usually an electrically operatedvalve such as an electric motor operated valve or an electrical solenoidoperated diverter valve. Some of the Voith and Transfluid fluidcouplings use fuse plugs in the outer periphery of their fluid couplingsand these fuse plugs melt during an over-temperature event, and must bereplaced by opening the external housing, or at least by opening a portin the external housing. Turbo Research, Inc. fluid coupling design usesan over-temperature switch to continuously monitor the circuit oiltemperature as it discharges through a series of orifice holes at theperiphery of the impeller or impeller casing, and in response to anover-temperature condition, this over-temperature switch causes anelectrically operated diverter valve to divert circuit oil from going tothe fluid coupling element and to bypass the circuit oil flow stream toan oil reservoir. After such an over-temperature event occurs, the fluidcoupling chamber evacuates, and the diesel engine can be caused to idle,which gives the various elements of the fluid coupling a period of timein which to cool gradually, avoiding excessively high thermally inducedstresses, particularly in the components of the rotating element. Voithand Transfluid also incorporate the function of an over-temperatureswitch to monitor the circuit oil as it discharges from the circuit,though there may well be a different method of effecting this function,and such switch causes an electrically operated diverter valve to changestate as described above upon sensing an over-temperature condition.With a fluid coupling in operation instead of a mechanical clutch, asthe mill becomes overloaded, the output speed of the fluid coupling andthe speed of the mill decrease substantially and in direct ratio to eachother, while the diesel engine speed either remains constant or declinesto a limited degree, but the diesel engine does not stop. In the case ofa fluid coupling and a manually controlled feedstock conveyor, as abovedescribed, the reaction time of the operator is still slow, andtherefore, it is still easy to jam a mill to a complete stop. However,with a fluid coupling with a circuit oil discharge temperature sensingdevice in service, if the circuit oil discharge temperature doesincrease above the pre-set trip point as occurs when the mill, theoutput shaft and attached runner stop, and the diesel engine andattached impeller will continue to rotate, while the fluid couplingsystem shuts down with no damage to the engine or to its components.

Turbo Research, Inc. developed fluid couplings with heavy duty steelimpellers, runners, and casings so that these fluid couplings can beengaged and disengaged at any engine speed, including full engineoperating speed, and can survive undamaged more severe over-temperatureevents than can be expected from fluid couplings made with cast aluminumcomponents, particularly those having cast aluminum components with thinvanes. Experience with the Turbo Research, Inc. fluid couplingsindicates that if the mill was not cleared and therefore is still jammedat the time that the fluid coupling is engaged, the circuit oil will gethot, the over-temperature switch will detect this and will trip thecircuit oil control valve so that the circuit oil is diverted, and thefluid coupling returns to the disconnected state, with no damage to thefluid coupling or to the drive train.

Today many fluid couplings are designed with some means for continuouslymonitoring the circuit oil as it discharges from the element, withover-temperature switches, and with electrically controlled circuit oilflow diverter valves, and have no wearing parts such as the mechanicalclutches have, have no resetable springs and detents such as themechanical torque limiters have, and have no fuse plugs such as werepreviously used in the Voith and Transfluid fluid couplings. For thisreason, it has been shown that the fluid couplings with theover-temperature switches and oil diverter valves are the lowestmaintenance clutch means available.

One advantage of the fluid coupling over a mechanical torque limiter isthat occasionally there are lumps in the feed stock entering the hammermill that are big enough to cause a mechanical torque limiter toseparate, even when set to separate at five times rated torque, butwhich can be chewed up and processed with a fluid coupling because thefluid coupling continues to transmit power in a substantially overloadedcondition for some period of time. During the time period of thisoverload condition, the temperature of the circuit oil and of the fluidcoupling continue to increase, but in that time period, hard lumps, ifnot too large or not too many, will be processed and the comminutingmill will clear itself. If the mill does not clear itself by the timethat the circuit oil discharge temperature reaches the trip set-point,the over-temperature switch causes the circuit oil to be diverted to areservoir, and the impeller-runner cavities will empty, thus reducingthe torque transmission of the fluid coupling to a minimum, so that thediesel engine becomes unloaded and can be shut down in a normal shutdownmethod without damage, so that in this manner, the fluid couplingfunctions as a torque limiting device.

In some cases, the mobile equipment drive train can be assembled with afluid coupling driven by an engine, the fluid coupling driving amechanical torque limiter, the mechanical torque limiter in turn drivingthe mill, for the specific purpose of having the fluid coupling benefitof being able to chew through overload conditions as well as for havingthe mechanical torque limiter benefit of minimizing damage to the millshould a large chunk of steel enter the mill and be hit by a hammercausing a great impact sufficient to separate the parts of themechanical torque limiter immediately thereby instantaneouslyterminating the power to drive the mill.

Voith and Transfluid typically manufacture the external stationaryhousings for their type (3) fluid couplings either as complete castingsor welded fabrications including the oil reservoir, and they use abearing arrangement with a bearing between the housing and the input endof the input shaft, two shaft bearings between the input and outputshaft assemblies to resist side loading, and one bearing between thehousing and the output shaft, so that one output shaft can be used fordual purposes: (a) mounting a flexible coupling hub for direct drive, or(b) mounting an overhung sheave with side loaded belts that does notrequire and does not permit a support bearing on the outboard end of thesheave. The Voith and Transfluid design with a bearing supporting theinput end of the input shaft requires some form of radial flexibilitybetween the input shaft of the fluid coupling and the flywheel of thediesel engine because there are substantial radial runouts in thenominal design of diesel engines, and consequently, this design uses aform of a Holset coupling with elastomeric elements between the couplingpart fixedly mounted to the flywheel and the coupling part fixedlymounted to the input shaft.

Turbo Research, Inc. developed a fluid coupling module that can be usedwith, and bolted to, any of several output power train assemblies suchas, for example, clamshell with sheave and outboard bearing for sideloads, direct drive housing with outboard bearing, parallel offset gearsand gear housing, and right angle gears and gear housing, wherein eachfluid coupling module and output drive train assembly use theappropriate output shaft for the fluid coupling runner and the specificdrive train selected. Further, the Turbo Research, Inc. fluid couplingsare designed with a bearing arrangement having two high capacitybearings supporting the output shaft and, in the case of the side loaddrive train, straddling the sheave or gear, and the inboard end of theoutput shaft, which is overhung into the fluid element cavity, supportsone inter-shaft bearing to one end of the input rotating assembly. Inthis design, the input end of the input shaft, impeller and impellercasing assembly is supported by a series of thin flexible diaphragmsthat, near the outer periphery, are fixedly bolted to the diesel engineflywheel, and near the inner edges, are fixedly bolted to the inputshaft, providing axial and angular bending flexibility between the inputshaft of the fluid coupling and the diesel engine crankshaft andflywheel assembly, and therefore, in this arrangement, the bearings ofthe diesel crankshaft functionally support the input end of the fluidcoupling input shaft and impeller assembly. The advantages of thisdesign include (a) the ability of the large straddle bearings of theoutput shaft to handle repeatedly extremely large side loads concomitantwith a jam of a mill, (b) a very substantial reduction in overall lengthprovided by the use of a flexible diaphragm disc coupling instead of aHolset style coupling between the flywheel and the fluid coupling inputshaft, which is beneficial to those applications where the axis of theengine and fluid coupling drive train is transverse the mobile equipmenttrailer, and therefore, perpendicular to the length of the drive train,and (c), due to (b), a reduction in the overall trailer width, reducingor eliminating the need for special permits for the trailer to travel onthe highways.

The diaphragm discs used in the subject fluid couplings are adapted fromdiesel engine driven electric generators made by Onan of Minnesota, inwhich application the diesel engine crankshaft and crankshaft bearingssupport through the flywheel and disc-pack the inboard end of anelectric generator. Individual discs are on the order of 0.040 to 0.060inches thick, and multiple discs are used in a disc pack, the number ofdiscs depending upon the torque transmitted. The discs are made by astamping process using accurate dies, and are commercially available.Such disc packs are radially stiff, have limited flexibility in relativeaxial displacement between the connected shafts, and are quite flexiblein angular bending between the connected shafts. Similar disc packs areused in a variety of flexible couplings connecting two adjacent shaftends, are available in many sizes, are sold under the trade name ofThomas, are made by Rexnord, and are also commercially available. Theapplication of a flexible disc-pack to a fluid coupling driven by adiesel engine as done herein has, to our knowledge, not been donebefore.

In the assemblies of a mobile equipment trailer having certaincombinations of equipment that include fluid couplings, allocations ofspace may be such that it is beneficial to have the reservoir locatedremotely from, yet at a level below, the bottom flange of the fluidcoupling. This can be accommodated with the use of a conduit ofsufficient diameter between the bottom flange of the fluid coupling andthe reservoir, and with a pump directly driven by an electric motor or ahydraulic motor. Preferably, the inlet to the pump is below the oillevel of the reservoir. The pump may be located in the reservoir orseparate from the reservoir.

SUMMARY OF THE INVENTION

In accordance with this invention, generally stated, a fluid couplingmodule is provided that incorporates an input (impeller) section and itsmeans for connection to a prime mover, a fluid coupling section, an oilpumping and oil conditioning system, including a reservoir and anincluded pump located vertically below the fluid coupling sections, andremotely mounted controls and control logic. This fluid coupling moduleis then common to output power train assemblies taken from the groupconsisting of a clam-shell housing, sheave and straddle bearings forside load; a straight-through drive housing and outboard bearing fordirect drive; a parallel offset gear and housing assembly; and a rightangle gear and housing assembly, whereby the same fluid coupling modulecan be employed by any of the output power train housing assembliesusing an appropriate output shaft for the fluid coupling runner andoutput power train assembly selected.

In the preferred embodiment, flexible diaphragm plates are fastened neartheir outer periphery to the fly wheel of a diesel engine, and neartheir radially inner edges to an outer end of an input shaft to theimpeller of the fluid coupling, whereby the input shaft is supported atits outer end by the flexible diaphragm plates and crank shaft bearingsof the diesel engine.

Also, in an assembly including a prime mover (generally a diesel engine)for driving a fluid coupling, a rotating comminuting machine such as ahammer mill, an output power train between the fluid coupling and thecomminuting machine, and a conveyor for feeding material into thecomminuting machine, the fluid coupling having an impeller and a runner,means are provided for measuring the slip speed between the impeller andthe runner, and for regulating the speed of the conveyor or, forexample, for regulating the speed of movement of the road grinder, inresponse to the slip speed relative to the set point slip speed.Preferably, the slip speed differential is calculated as a percent,whereby the regulation is substantially independent of the running speedof the prime mover. The means for regulating the speed of the conveyor,for example, can include a multi-toothed wheel and a mating speedpickup, mounted on the output shaft of the fluid coupling, a signal fromthe engine speed detector such as is used by the engine speed governor,and an electronic controller with suitable programming, whereby theelectronic controller modulates the speed of the feed stock conveyor inorder to maintain the slip speed of the fluid coupling at a preset setpoint value, for example 2.5% or 3%, with the preset set point valuebeing selected to optimize the production according to certainobjectives desirable to the operator, such as chip size, type ofmaterial being processed, tons processed per gallon of diesel fuel, orsimply, tons processed per operating hour. An advantage of using theslip speed to control the conveyor speed arises from the development ofnew engines and controls. In older diesel engines, the governors, whichcontrolled fuel flow to maintain a pre-set engine speed, were primarilymechanical in nature, and permitted some droop in the speed of theengine in response to an increase in the load. In this situation, theconveyor can use the droop of the engine speed as an indicator of load.In newer engines, the governors or fuel flow controllers, are veryprecise and can maintain a given speed with almost no droop in actualengine speed over the entire load range until the full fuel flowcondition is reached, and for further increases in load, the speeddroops dramatically. For this type of governor, engine speed is almostof no value to control the conveyor speed because there is no speedchange until overload condition occurs, which is what is trying to beavoided. Then, an overload of feed stock is what causes the engine to gointo overload condition and the speed to droop, but the overload hasalready occurred and could not be detected until after the fact. With afluid coupling, the slip speed is directly related to torque transmittedin a linear relationship: if there is no torque transmitted, there is noslip. As the load increases, the slip increases, so with the slip speedas the measure, it is now easy to determine the degree of loading of thepower train and the approach to an overload condition can be detectedbefore it occurs, even though the engine speed remains constant oralmost constant over the entire load range up to the point of overload.Hence, for either the mechanically controlled governors or the newerelectronically controlled governors, the slip speed of the fluidcoupling provides a better indicator of load and a better indicator ofapproach to an overload condition than was heretofore available witheither type of governor. Alternatively, because the speed of the outputshaft is a function of the slip speed, in that the greater thedifferential in speed between the input and output shafts, the greaterthe slip speed differential, a multitoothed wheel mounted on said outputshaft and a mating speed pickup can be used to control the speed of theconveyor, whereby the speed of the conveyor is a function of the speedof the output shaft. An electrical or electronic speed determiningdevice can be used instead of the multitoothed wheel.

In the variable speed method of the present invention for controllingthe feed stock conveyor, the feed stock conveyor can at times be drivensubstantially faster than the present common fixed conveyor speed,because most of the time the mill is under-loaded, so that speeding upthe conveyor when it is under-loaded and the slip speed is below the setpoint slip speed will send up more feed stock into the hammer mill in agiven period of time. Then when the hammer mill is heavily loaded sothat the actual slip speed, for example, 3.7%, is larger than the setpoint slip speed, say 2.5%, then the controller slows down the conveyor.Control programs using PID (proportional, integral and differential) arereadily available and are well known by control designers today. Anotherreason for using slip speed is that the engine speed is variable and canbe set anywhere in the range of 1800 to 2300 rpm, for example, dependingupon several variables, including the type of material available, itscondition, and the size of the chip desired to be made. In any case,modulating the rate of feed into the mill in order to maintain a givenslip ratio will optimize the tons milled per hour and the tons milledper gallon of diesel fuel used, and will keep engine load in normaloperating range for a greater portion of the operating time, therebyminimizing air pollution due to abnormal fuel/air ratios.

Input and output shafts of the fluid coupling are oriented substantiallyhorizontally. A removable reservoir, located vertically below the levelof impeller and runner casings and input and output shafts, contains acirculating oil pump within the reservoir, positioned with an intakesubmerged in circulating oil, so as to be self priming. The circulatingoil includes both circuit oil, which fills impeller and runner cavities,and lubricating oil for the bearings. A heat exchanger for thecirculating oil is provided with a vent line at its top communicatingwith the oil reservoir to ensure that the heat exchanger does not becomeair locked. A temperature control valve is provided to mix cooled oilfrom the heat exchanger with hot oil that bypasses the heat exchanger toprovide oil at a preset temperature to the fluid coupling. A filter isprovided to assure that no significant particulate matter enters thebearings. A heating element is provided in the oil reservoir to warm theoil prior to starting the fluid coupling and the diesel in cold weatherconditions. An electrically actuated control valve is provided as an oilflow diverter valve that directs circuit oil into the fluid couplingelement when the signal to engage the coupling is given, and anover-temperature sensor is provided such that when the temperature ofthe circuit oil leaving the element exceeds a preset set point value, asoccurs when the mill jams, the sensor sends a signal to the controllerand on to the diverter valve to divert the circuit oil to the reservoir,thereby permitting the impeller and runner cavity to evacuate, whichseparates the engine from the load, and the engine can then be broughtto idle and cooled down and shut down in a normal manner without damageto any part of the entire power train, and in so doing permit the entiretrain to be brought back into service after the mill is cleared. Theoperation of the diverter valve does not affect the operation of thebearing oil lubrication system, which continues as long as the impellercasing is rotating.

By making the fluid coupling a part of a module that includes the fluidcoupling housing, the reservoir and its pump, the diverter valve, heatexchanger, temperature control valve, filter, piping, and controlsincluding a programmable controller for the feedstock feeding process,and by providing for bolting to the output shaft end of the housingvarious forms of power train, including the clam-shell housing with beltsheave, the module can be supplied to a manufacturer as a unit, for usewith whatever type of power train is required.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Referring now to the drawings for illustrative embodiments of thisinvention,

FIG. 1 is a fragmentary view in side elevation, partly in longitudinalsection and partly broken away of a portion of one embodiment of theassembly of this invention;

FIG. 2 is a view in elevation of the input end of a module shown insection in FIG. 1;

FIG. 3 is a somewhat diagrammatic view in perspective of a dieselengine, showing a hydraulic pump and a module of this invention withouta clamshell housing and with an external bearing support, merely toillustrate the tending of belts from a sheave shown in FIG. 1;

FIG. 4 is a diagrammatic view in perspective, partly expanded, of ahammer mill and feed conveyor and its hydraulic motor;

FIG. 5 is a diagrammatic view of an oil system applied to a module ofthis invention shown in side elevation;

FIG. 6 is a fragmentary view in cross section of a second embodiment ofa coupling assembly between a runner and an output shaft;

FIG. 7 is a schematic view of an entire assembly of this embodiment ofthe invention;

FIG. 8 is a schematic view of an electrical/hydraulic control circuitfor regulating the speed of a feed conveyor;

FIG. 9 is a somewhat schematic view in section of a gear box connectedto an end plate of a module of this invention; and

FIG. 10 is a somewhat schematic view in section of a direct driveconnected to an end plate of a module of this invention; and

FIG. 11 is a somewhat schematic end view of a fluid coupling with aremote oil reservoir of this invention.

DETAILED DESCRIPTION OF INVENTION

Referring now to the drawings, particularly FIGS. 3, 4, and 7, referencenumeral 1 indicates an entire assembly, including a diesel engine 3 witha hydraulic pump 110 with hydraulic lines 158 and 160 with a hydraulicoil reservoir RR, a fluid coupling 5, a conveyor 9 with hydraulic motor109 with hydraulic lines 163 and 164, accompanying hydraulic controls 10driven through a communication channel DD by programmable electroniccontrols 11 with electronic input signal lines 150, 152, and 162, and ahammer mill 12 with driving belts 108.

As is shown in FIG. 1, the fluid coupling 5 has a housing 14, with agenerally cylindrical outer wall 15 and a flanged area FF at its bottomto which a reservoir 75 is mounted. At an impeller end of the housing,is an inner wall 17. At a runner end, a heavy wall or center housingplate 18 is bolted to the housing outer wall 15. The plate 18 has acircle of interiorly threaded bolt-receiving bosses 19 openingoutwardly.

The diesel engine 3 has a crankshaft CR, crankshaft bearing 20 andflywheel 21. In the illustrative embodiment shown, diaphragm flex plates25 are bolted through holes in a circle near the outer edge of theplates with bolt and washer assemblies 26 to the flywheel 21, and,through a circle of holes near an inner edge of the plates with bolt andwasher assemblies 29, into a hub 34. Long bolts 32 pass through hub 34,through an impeller shaft 28, and into a boss of an impeller 35. Betweenthe inner wall 17, and the impeller 35, a circuit oil nozzle 36,attached to inner wall 17, is adapted to supply circuit oil to animpeller oil pump 37, attached to a back side of the impeller 35, andcommunicating through passages 38 with the interior of the impeller. Anarrow on FIG. 1 delineates the flow path of circuit oil from theexternal supply pipe (not here shown), through passages in the innerwall 17, through the nozzle 36, into and through the impeller oil pump37, through passages 38, and into the impeller 35.

The impeller 35 has vanes integral with its interior surface. Theimpeller is bolted to an impeller casing 40, which surrounds a runner45. In this embodiment, the mating surface between the impeller casingand the impeller is offset in a direction toward the input end from theplane of the gap between the impeller casing and the impeller, as shownin FIG. 1. This reduces the stresses in the faces of the vanes of theimpeller induced by the centrifugal forces of the oil in the impellercasing, hence, on the impeller, when the circuit is full of oil, theobjective being to reduce the possibility of cracking of the vanes. Theimpeller casing 40 is supported by a bearing 60 mounted on an outputshaft 50. The output shaft 50 is bolted to a runner 45 with bolts 51, inthis embodiment. The output shaft 50 is supported by a spherical rollerradial bearing 55 mounted in an opening in the center housing plate 18.Radial passages 39 in the periphery of the impeller casing 40 have areplaceable orifice plug or fitting 41 to permit a predetermined amountof oil from the impeller and runner cavities to pass through the orifice41 and into housing 14, wherein, in this embodiment, the flow divides,the larger portion flowing through port 74 at the bottom of the housinginto the reservoir 75, and a smaller portion flowing into a trough 92,into which a temperature sensor 91 extends, through a small port 73 inthe trough 92, into the reservoir 75. The size of the orifice plug 41selected may be increased to increase the rate at which the cavitiesevacuate after the control valve is turned to bypass, but must be smallenough to assure that a portion of the circuit oil overflows throughaxial passages 71 in the impeller casing 40 to provide a full circuit ofoil in normal operation. The oil overflowing through passages 71 joinsthe bulk of the oil flowing from orifices 41 through port 74 intoreservoir 75. Axial passages 69 extend from the interior of the runnerto the chamber between the runner 45 and the impeller casing 40, nearthe innermost end of the runner cavity. The primary purpose of thepassages 69 is to provide venting of the interior chambers of theimpeller and runner in order for air and oil vapor as well as oil topass freely to avoid vapor locking the inner cavities. For the oilflowing out of the passages 71, the principal flow path is through a gapGG between the face of the runner at its periphery and the opposed faceof the impeller, through the gap between the inner surface of theimpeller casing 40 and the outer surface of the runner 45, and exitingthrough passages 71 into the housing 14. Additionally, any oil passingfrom the runner cavity through passage 69 can also exit through passages71 into the housing 14. Oil in the housing 14 from both the axialpassages 71 and the orifice passages 39 is substantially a foam, thatis, a mixture of oil and air, and it partially detrains as it drainsalong path 72 through an opening 74 in the bottom of the housing 14,into the reservoir 75 fixedly attached to the flange FF which is anintegral part of the outer wall housing 14. The level of oil LL in thereservoir is set as close to the top of the tank as possible consistentwith oil draining back from the heat exchanger and other equipmentwithout overflowing when the engine is stopped. The oil level drops whenthe fluid drive is in service, because the oil fills all of thestationary equipment and the rotating fluid coupling element. Anobjective in sizing the reservoir is to have a volume of oil containedin the reservoir that is typically equivalent to the flow of oil pumpedin 45 to 60 seconds, because this residency time normally is adequate todetrain sufficiently the oil for fluid coupling service.

A circulating oil pump 76 is positioned within the reservoir with aninlet 79 that is below the level of oil LL in the reservoir so as tomake the pump self priming. In most fluid coupling service, positivedisplacement pumps are used because they can handle oil that containsfoam, that is, oil that contains a portion of air, generally up to 10%and sometimes up to 15% air. The air in the oil is compressed in the oilas it passes through the pump, thereby maintaining the same mass flowrate of the oil, but decreasing the volumetric flow rate in proportionto the air contained in the oil at atmospheric, or suction, pressure.Air can also exit (or enter) the oil in the impeller and runnercavities, depending upon the degree of turbulence, and exit (or enter)through passages 69 and 71, as required. In this embodiment, the pump 76is mounted on a slidable plate 82, which can slide vertically in slotsin the interior surfaces of a pair of symmetric support brackets 83 thatare fixedly mounted to flange FF by bolts. The pump is chain driven bymeans of a drive sprocket 80 attached to the impeller casing 40, adriven pump sprocket 78 that is mounted on the pump drive shaft andaligned axially to the drive sprocket 80, and a chain, not shown, thatruns between the drive sprocket 80 and the pump sprocket 78. In theembodiment shown, a spaced “L” shaped wall 68 made of thin metal isattached to the ends of the symmetric slotted support brackets 83 sothat the lower end of the wall almost contacts, or does contact, thesliding plate 82 at a distance below the reach of the pump sprocket 78,so as to form a pump sprocket well, isolating the pump sprocket from thebulk of the oil in the reservoir to reduce agitation of the oil by theaction of the chain and pump sprocket. An internal oil supply linecomprising a flexible hose 185 is connected to a pump discharge port 179at one end and at another end to a fitting CCC. The entire movable pumpassembly comprising pump 76, slidable plate 82, and sprocket 78, aremoved to provide proper tension to the chain, and locked in place bytightening bolts 183. Vertical jack bolts YY and lock nuts YYY can beused to aid in adjusting the tension of the chain. In the embodimentshown here, oil reservoir 75 is mounted to flange FF of the housing 14.After the pump is mounted, hoses are attached, the chain is tensioned,and the sprocket well plate is attached. In an alternate embodiment,suitable access ports in the top of the reservoir can be used to allowthe manipulation of the pump assembly and the loosening and tighteningof the bolts holding the sliding plate, as well as connecting one end ofa flexible hose to the pump discharge port 179 and the other end to afitting, similar in function to CCC, for passing oil to the outside ofthe fluid coupling, which fitting may be mounted on any surface of thereservoir as suits the application.

A heater and thermostat 77 in the reservoir conditions the circuit oilin the reservoir when the ambient temperature is too low.

Referring now to FIG. 5, an oil system 84 includes an internal oilsupply line 185 from the pump 76 to a fitting CCC, an external oilsupply line 85, a pressure relief valve BBB with a return line to thereservoir 75, a heat exchanger 86 which has a vent line 87 at itsuppermost point to vent trapped air to the reservoir 75, a temperaturecontrol valve ZZ, a filter 88, an oil header 117, a back pressureregulating valve PRV, an oil flow diverter valve 89, operated by anelectrical actuator 90, from which a circuit oil line 115, typically onthe order of1–¼ inch or larger pipe and conducting 20 to 40 gallons perminute, is connected to a fitting to a pipe leading to the nozzles 36. Achoke CB may also be used to maintain pressure in the oil header 117during normal operation. Large diameter pipes are used for the high flowconduits to reduce the velocity in order to reduce the heating of theoil that occurs when high velocity, turbulent oil passes through smalldiameter pipes. A circuit cooling oil conduit 95, relatively small indiameter as compared with the circuit oil line 115, is tapped into theoil header 117, and bypasses the diverter valve 89. The circuit coolingoil conduit 95 provides cooling oil to remove the heat generated bywindage, when the impeller and runner are evacuated of a normal flow ofcircuit oil. To this end, a choke in the form of a small orifice 98 maybe provided in the circuit cooling oil conduit 95 to limit the flow forbypass circuit operation. Also, from the diverter valve 89 a bypass oilline 94 extends that opens into the reservoir 75. The by-pass oil line94 may also have a choke in the form of an orifice 99 between thediverter valve and the reservoir, to provide backpressure to the oilheader 117. Lube oil line 96 from the oil header 117 provides lube oilto the bearings 60 and 55. Lube oil line 96 is relatively small comparedto circuit oil line 115, and a choke CA may be used to control thebearing lube oil flow, typically on the order of 1 to 2 gallons perminute. In certain applications, for example, when there is a wideoperating speed range of the diesel engine and the pump speed isdirectly controlled by fluid coupling input speed, a back pressureregulating valve may be preferred to maintain a relatively uniform oilsupply pressure for the bearings, and chokes 99 and CB are not used. Inother applications, the diesel engine operating speed and ambienttemperature conditions may be quite uniform and a backpressureregulating valve may not be needed.

The function of the temperature control valve ZZ is to mix the cooledoil from the heat exchanger and the uncooled oil that bypasses the heatexchanger in proper portions to provide a supply of oil to the fluidcoupling at the specified temperature set point. In certainapplications, it may desirable for all of the oil to be cooled all ofthe time, and a temperature control valve is not required.

The temperature sensor 91 extends through a wall of the housing 14, andinto the trough 92 through which oil being discharged from the impellerpasses. The temperature sensor 91 is electrically connected to operatethe electrical operator 90 of the diverter valve 89.

A control panel EE contains instruments such as oil header temperaturegage, oil header pressure gage, circuit oil discharge temperature gageand circuit oil discharge over-temperature switch which functionallycauses the oil diverter valve 89 to operate when an over-temperatureevent occurs. FW Murphy Company of Oklahoma manufacturers a combinedtemperature gage and over-temperature switch in one instrument, and thisuses a remote sensor operating on the Bourdon tube principle, with thesensor located in port 91 and the instrument located in the controlpanel EE. Another type of over-temperature detection device, known as aKaiser switch, is a combined switch and sensor, and it is directlylocated in port 91 with a wire leading to it from the control panel.Another type of over-temperature device, also made by FW Murphy, is aninstrument that displays temperature, contains over-temperature switchfunction and is driven by a thermocouple remotely mounted in port 91.

The Bourdon tube gage and switch device and the Kaiser switch device arecommon on much power transmission equipment including fluid couplings.However, over-temperature events, depending upon the temperaturereached, can cause a Bourdon tube device to expand inelastically anddevelop an offset. While the Kaiser switch is a unitized instrument andhas the appeal of simplicity, the switching part of the instrument isnot capable of withstanding repeated extreme over-temperature eventseither.

Because the fluid couplings that are the subject of this application aremade entirely of steel or ductile iron, they can handle over-temperatureevents that are beyond the capability of those made using aluminumcomponents, and therefore, there is a need for over-temperature sensingand switching devices that are capable of surviving repeatedlyover-temperature events with very high temperatures, on the order of 400to 450 degrees Fahrenheit. A display and switching instrument driven bya thermocouple mounted in the port 91 is not affected by suchover-temperature events because such systems can easily handle eventsover 1000 degrees Fahrenheit, or higher, depending upon the materialsused to make the thermocouple, far higher than is expected to beexperienced in a severe over-temperature event by any fluid coupling.This type of thermocouple driven temperature sensing, display andswitching instrument is commonly found in fluid drives throughout thepower generation industry, but heretofore, it has not been used in fluidcouplings in the mobile equipment industry.

In the case of a massive jam, the oil in the fluid coupling will becomeoverheated with respect to the set point of the temperature sensor andthe entire coupling will be evacuated, preferably in no more than 15seconds, by virtue of the operation of the diverter valve 89 and thepassages 39 and orifice plugs 41. The filling rate on start-up ispreferably about 45 seconds.

In the illustrative embodiment shown, the center housing plate 18 isbolted to the external housing 14 by bolts 23, and a clamshell housing100 is bolted to the center housing plate 18 by bolts 104, threaded intothe bosses 19 of the plate 18. The clamshell housing 100 houses a sheaveor multiple sheaves 105, mounted on the output shaft 50. The shaft 50projects through the clamshell housing 100 and is journaled in a rollerbearing 102, carried by an end plate 101, which can be either integralwith the clamshell housing 100 or separate and bolted to the clamshellhousing. The side wall of the clam-shell housing 100 is open through asubstantial arc, to admit belts 108 extending around the sheave 105, andleading to a sheave on the hammer mill 12. Because the boss pattern ofthe bosses, hence the bolt pattern of the corresponding bolts of theclam-shell housing, is circular and of uniform angular spacing, theclam-shell housing can be oriented in any desired angular directionpermitted by the bolt spacing, to permit the belts to extend vertically,horizontally, or somewhere in between, as the position of the hammermill relative to the fluid coupling requires. As has been indicated, thebosses 19 are designed to permit the bolting to the plate 18, hence tothe fluid coupling module, of a wide variety of power transmissionelements. Some different kinds of power transmission elements willrequire different output shaft configurations, but the appropriateoutput shaft will be supplied in most cases by the manufacturer of thefluid coupling, so that the recipient of the module has only to bolt onthe power transmission element. In the case of complex coupling systemssuch as a gearbox, the output shaft can have a configuration to attach agear shaft, or alternatively, the gear manufacturer can provide a gearshaft to the fluid coupling manufacturer for assembly. A gear box 200,shown somewhat schematically in FIG. 9, and a direct drive 222, alsoshown somewhat schematically in FIG. 10, are merely illustrative ofdrive trains that can be accommodated by the module of this invention.

Referring now to FIGS. 1, 7 and 8, between the outer end of the sheave105 and the end plate 101, a multi-toothed wheel 107 is mounted on theoutput shaft, which mates with a speed pickup 106 that provides outputshaft speed information, through wire 152 to the control 11 thatcontrols the speed of the conveyor 9. The conveyor 9 is driven by ahydraulic motor 109, supplied with hydraulic fluid under pressure by apump 110 driven by the diesel engine 3. The speed of the hydraulic motor109 is controlled by the flow rate of hydraulic fluid supplied to it,which in turn, is dependent on the control of a control valve 10 that isregulated by a computer 11 that is programmed to be responsive to, amongother things, the output shaft speed pickup signal from sensor 106, asis well known to those skilled in the art. A schematic of a suitablecontrol system is shown in FIG. 8. Alternatively, the hydraulic pump canbe driven by an electric motor, the speed of which can be regulatedfunctionally by the computer 11, or the conveyor itself can be driven bya variable speed electric motor, through a gear box of some sort, withthe variable speed electric motor regulated functionally by computer 11.

In FIG. 8, the hydraulic control valve (control 10) is shown as beingcontrolled by a PID programmable computer (control 11) usingcommunication channel DD. An electric signal indicating actual enginespeed is transmitted to the computer 11 through a line 150; and anoutput speed signal from the fluid coupling output shaft is transmittedthrough a line 152, by which signals the differential slip speed isdetermined by the computer 11. Various fixed input data, indicated bythe box 154, are stored in the computer, such as a slip speed set point,a minimum output shaft speed (which determines if the direction of theconveyor is to be changed, or the system shut down), and depending uponthese various criteria and the programming, an output signal from thecomputer is transmitted to the control valve 10, to which a highpressure hydraulic fluid line 158 from the pump 110 is connected andfrom which a return line 160 extends to a reservoir RR which supplieshydraulic fluid to the pump 110. Hydraulic oil lines 163 and 164function to deliver oil and to return oil to and from the motor 109 andvalve 10, depending upon the direction of rotation of the motor 109. Afeedback signal indicating the actual conveyor speed, forward andbackward, is transmitted from a sensor on the hydraulic motor 109 to thecomputer 11 through a line 162.

Programs used in controller 11 may have many features, selectable bydata entry during operation, depending upon the objectives of theprogrammer and, for example, the types of sensors used, the numbers ofsensors used, the types and capabilities of the conveyor, the abilitiesto open and to close the opening, or mouth, of the mill, the design ofthe hammers, whether fixed or swinging, the feedstock, and the desiredchip size.

A very simple program could have, for example, three discreet forwardspeeds, one reverse speed, and stop for the conveyor, controlled only bythe fluid coupling output speed, such that when the output speed isabove a preset set point, the conveyor goes at the fastest speed, whenthe fluid coupling output speed is at the set point speed or in a verynarrow range around the set point speed, the middle conveyor speed isused, when the output speed is below the set point speed, the slowestconveyor speed is used, and when the conveyor speed is below a secondset point speed, the conveyor goes into reverse, and when the fluidcoupling output speed is below the second set point for more than aspecified period of time, the controller functionally sends a signal tothe diverter valve, and the oil flow is diverted and the fluid couplingstops transmitting torque, the conveyor stops, the engine is shut downin an orderly manner, and the mill is cleared.

Alternately, the program can be written so that the computer calculatesslip speed from the engine speed via input speed signal 150 and from thefluid coupling output speed via signal 152, and provides discreet speedcontrol for the conveyor speed based upon slip speed and slip speed setpoint such that when the slip speed is near zero, the fastest conveyorspeed is used, when the slip speed is at or very near the set point slipspeed, the normal conveyor speed is used, when the slip speed is greaterthan the slip speed, the slowest conveyor speed is used, when the slipspeed exceeds a second set point speed, the conveyor reverses, when theslip speed exceeds the second set point slip speed for a period greaterthan a specified time period, the controller functionally sends a signalto the diverter valve and the circuit oil flow is diverted, the fluidcoupling stops transmitting torque, the conveyor stops, the engine isshut down in an orderly manner, and the mill is cleared.

As another alternative, the computer program can be written to calculatethe slip speed percentage, being the slip speed divided by the inputspeed and expressed as a percentage, with the same control over theconveyor being provided as a function of slip speed percentage ratherthan slip speed. By using a percentage of the slip speed as thecriterion, the operation of the control is largely independent of theengine speed which could be set anywhere in the range of 1800 to 2300rpm, depending largely on engine nominal speed range.

Alternately, the program can be written to provide variable speedcontrol of the conveyor according to output shaft speed, slip speed, orslip speed percentage, though the preferred parameter is slip speedpercentage, such that, for example, the conveyor speed is inverselyproportional to the slip speed wherein when the slip speed percentage iszero, or almost zero, the conveyor is at the fastest conveyor speed;when the slip speed percentage is at the preset set point, the conveyorspeed is at the normal conveyor speed, and when the slip speedpercentage varies above or below the set point percentage, the conveyorspeed decreases or increases smoothly and linearly in an inverseproportionality to the slip speed percentage. When the fluid couplingslip speed percentage increases above another preset setpoint, then theconveyor goes into reverse and when the slip speed percentage decreasesbelow the second setpoint, the conveyor resumes forward motion at aspeed determined by the current fluid coupling slip speed. Should theslip speed percentage remain above the second setpoint for a periodexceeding a specified time period, then the control 11 functionallycauses the diverter valve to divert oil from the fluid coupling, thefluid coupling terminates transmitting torque, the conveyor stops, theengine is stopped is a normal manner, and the mill is cleared.

Additionally, other functions of the feedstock feeding apparatus, suchas mill mouth opening, can be controlled in similar ways to the abovedescriptions for control of conveyor speed.

Referring now to FIG. 11, an oil reservoir 201 is shown remotely mountedfrom fluid coupling housing 14, and connected to the fluid coupling by aconduit 202. Conduit 202, which may be flexible or rigid to suit thearrangement, is fixed at one end to flange FF and fixed at the other endto flange 203 of the oil reservoir, and is sized to suit the flow,elevation difference and distance between the fluid coupling andreservoir. The reservoir may be shaped to suit the space available, andmay be sized to contain more oil than would be possible if the reservoirwere attached to the fluid drive mounting flange FF. In thisarrangement, the oil pump 211 is driven by a motor 212, either electricor hydraulic, oil is supplied to said pump via a suction line 215 andoil is discharged by line 216 that connects to line 85 of the oil system84 described above and shown in FIG. 5. In this embodiment also, theinlet to the pump is below the level of oil in the reservoir, therebymaking it a self-priming pump, which is preferred, though pumps mountedabove the oil level of the reservoir do function so long as a prime isachieved or retained.

There are occasions when it is desirable to disassemble the rotatingelement of the fluid coupling completely. Referring to FIG. 6 for animproved design that makes such disassembly possible so that all partsare reusable, as compared with the arrangement shown in FIG. 1, aremovable hub 190 is provided between the runner and output shaft 50,bolted to the runner by bolts 191, with dowel pins not here showninterspersed between bolts 191, and bolted to the output shaft 50 bybolts 194, with dowel pins not here shown interspersed between bolts194, and the direction of bolts 192 that attach the driving sprocket 80to the impeller casing 40 is reversed as compared with the bolts shownin FIG. 1 as securing the driving sprocket to the impeller casing. Thebolts 192 are threaded into tapped holes in the driving sprocket 80.These changes permit removal of the impeller casing, sprocket, and ballbearing 60 without removal first of the bearing 55 from the outputshaft, which requires great heat to accomplish. Bearing 55 is installedon the output shaft with a significant interference fit, which can beaccomplished by heating slowly, as in an oven or by an induction heater.However, to get this bearing and center plate off the shaft, in thedesign shown in FIG. 1, requires considerable heat applied quickly tothe bearing 55 and because this bearing can be heated from only theoutput end, the bearing is almost certain to be overheated and of nomore usefulness. With the use of the runner hub 190, the runner andrunner hub can be removed easily, and with the reversal of the directionof bolts 192, the impeller casing 40 can be removed from bearing 60 withheat without damage, then bearing 60 can be heated relatively quicklyand without overheating, and removed without damage, the sprocket 80 andsleeve SL can be removed easily, the center plate 18 can be heated andremoved easily, leaving bearing 55 exposed. The bearing 55 can then beheated from its outside diameter and both sides simultaneously,relatively quickly but without overheating, to permit its removalwithout damage.

Numerous variations in the construction and operation of the apparatusof this invention, within the scope of the appended claims will occur tothose skilled in the art in the light of the foregoing disclosure.Merely by way of example, although the module of this invention hasparticular utility in use with a diesel engine, other prime movers canbe employed. As has been indicated, the fluid coupling can be used todrive apparatus different from a hammer mill. The internal piping of themodule can be changed to suit the needs of the device, and thedimensions of such elements as the orifices in the lines and thepassages through the impeller casing, runner and casings can be varied,again, to meet the requirements of the particular machine or task, asfor example, to increase or decrease the fill time and the emptying timeof circuit oil, or the temperature limits of the circuit oil temperaturesensor. The runner hub can be made integral with the runner. The radialpassages 39 can be made in the impeller rather than in the impellercasing, although the arrangement described is preferred, for the reasonsgiven. The circulating oil pump in the reservoir can be driven by a geartrain from a gear on the input shaft, or the pump can be removed fromthe reservoir and mounted externally and driven by an electric motordirectly or by the diesel engine directly, In any case, the intake tothe pump should be below the level of oil in the reservoir, to make thepump self priming. The same diesel engine that powers the fluid couplingcan be employed to run a generator to provide electricity to power theoil pump motor or the conveyor motor, or both, as has been indicated asalternatives to the chain or gear drive, or hydraulic motor drive to thepump motor, or the hydraulic motor to power the conveyor. Thesevariations are merely illustrative.

1. In a fluid coupling connected to a flywheel of a diesel engine which drives a mobile piece of equipment, the fluid coupling having an impeller with an impeller casing connected to an input shaft and a runner connected to an output shaft, said input and output shafts being oriented substantially horizontally, said impeller being driven by a diesel engine, a reservoir and a circulating oil pump located in said reservoir, said reservoir being positioned vertically below the level of said impeller and runner casings and said input and output shafts, said oil pump being a part of a circulating oil system, a heat exchanger operatively connected in said circulating oil system, the improvement comprising a vent pipe in a top of said heat exchanger and communicating with said oil reservoir, whereby to vent said heat exchanger.
 2. The improvement of claim 1 including a filter through which all of the oil passes that is going to the fluid coupling, the filter removing all particulate matter larger than a specified size.
 3. In a fluid coupling connected to a flywheel of a diesel engine which drives a mobile piece of equipment, the fluid coupling having an impeller with an impeller casing connected to an input shaft and a runner connected to an output shaft, said input and output shafts being oriented substantially horizontally, said impeller being driven by a diesel engine, a reservoir and a circulating oil pump located in said reservoir, said reservoir being positioned vertically below the level of said impeller and runner casings and said input and output shafts, said oil pump being a part of a circulating oil system, a heat exchanger operatively connected in said circulating oil system, the heat exchanger comprising a vent pipe in a top of said heat exchanger and communicating with said oil reservoir, the improvement comprising a heating element located in said reservoir, to heat the oil in cold start conditions.
 4. The improvement of claim 3 including a thermostatic control of said heating element. 